Research is proposed which will characterize the enzymes involved in the conversion of urea to ammonia and carbon dioxide. In the yeast Candida utilis, one of the organisms under study, this activity resides in one physical entity and is referred to as urea amidolyase. In the alga Chlamydomonas reinhardii, the other organism used in this study, this activity is carried out by two distinct enzymes, urea carboxylase and allophanate hydrolase. These enzymes are, collectively, referred to as urea amidolyase. The comparison of these enzyme systems will include pH influences, molecular weight determinations, influence of inhibitors, determination of types of reactions catalysed, as well as other properties.